1. Field of the Invention
The present invention relates to a plate making system for printing abstract patterns and especially sand patterns on construction materials, and to printed matter printed by use of plates made by that plate making system.
2. Description of the Prior Art
Today, there is a growing awareness that natural construction materials such as timber are getting scarce. To meet the demand for such materials, alternative materials such as plywood and gypsum board have been developed. The surface of these artificial materials is usually decorated with printed matter. The importance of such printed matter is growing in terms of both decorative and protective roles it plays.
Patterns of the printed matter on construction materials fall into two major groups: a natural pattern group comprising such naturally occurring patterns as wood and stone texture patterns, and an artificially created abstract pattern group including geometric patterns, ground tint patterns, floral patterns and so called sand grain patterns. Sand grain patterns refer to that kind of pattern and its modifications which is obtained by conceptually sprinkling numerous sand grains over a monotone surface of paper or like material.
Sand grain patterns are printed on construction materials conventionally by one of three methods. For any of these methods, a sand grain pattern is created first, followed by the making of a plate based on that pattern.
The first prior art method involves collecting sand grains, sprinkling them over a monotone paper surface of the like to create a sand grain pattern, photographing the pattern, and manually making a plate of the pattern by photo-etching. The second prior art method involves having a scanner read from a film of the photo image created by the first method and making a plate of the image by electronic gravure-engraving. The third prior art method involves electronically generating sand grain patterns. More specifically, a given number of sand grains are randomly generated and arranged in an image memory using a random number. The pattern thus generated is made into a plate by electronic gravure-engraving.
With sand grain patterns as well as other abstract patterns, some unforeseen pattern deviation may emerge and become visible at the proof printing stage or running-on stage. In such a case, a repetitive pattern unintended by the designer or pattern creator appears, sometimes more pronounced than the original pattern. This is a major problem with the three prior art methods when any of them is used to create sand grain patterns.
The unintended repetitive pattern, if it occurs, is a fatal flaw of construction materials with printed abstract patterns. Checks are carried out to make sure that such patterns do not occur throughout the process up to the running-on stage. Should any unintended repetitive pattern be recognized, it is removed by the operation generally known as retouching. Retouching is a wholly manual process that requires a great deal of experience and expertise. The process is subject to heavy work load, is time-consuming, and not always effective in completely eliminating latent undesirable patterns. In particular, because the sand grain pattern is a collection of dots that are minuscule binary images, removing one unintended repetitive pattern often gives rise to another such pattern. Completely removing those undesirable repetitive patterns is a difficult task to achieve.
The third prior art method mentioned above has an additional problem to contend with. If the accuracy of random number generation is relatively low or if the number of grains or used random numbers is very large despite a high level of accuracy in generating the random number, unintended repetitive patterns are more liable to occur.